At present, it is a problem that during strand and cord construction, using e.g. double or single twisting operations, filaments of the strand or cord break. Most frequently, such ruptures cause two loose ends of filament, which projects out of the profile of the strand or cord.
The loose filament ends of the strand or cord may cause problems when the strand or cord is used during subsequent processes.
When such strand with projecting filaments is used to provide a multi-strand cord, these projecting filaments may cause process problems during cord production. The projecting ends may cause congestion in eyes, guiding parts or on small passages.
Due to this interaction between machinery parts and the filament ends, the broken or interrupted filament may “sleeve off”. Over a large length of the strand, the filament is pulled out of the strand.
When strands as such or cords with projecting filaments are used, e.g. as control cables, these projecting filaments may cause disorder of the process in which it is used.
When such strand or cord with projecting filaments is used to provide polymer or rubber products (e.g. timing belts, elevator or hoisting belts), the projecting filaments may cause shearing or disfunctioning of the polymer or rubber matrix. Also here the projecting ends may cause congestion in guiding parts of e.g. extrusion machinery or other machines processing the strands or cords.
Therefor, such strands or cords with broken filaments or with filament ends projecting out of the profile of the strand or cord are avoided.
In order to avoid such projecting filaments, metal strands or cords, comprising such projecting filament ends, may be cut into two at the location of the projecting filament ends. As a result, a strand or cord with a length being the length of the strand or cord before the filament rupture is provided.
Either strand ends or cord ends may be welded one to another, providing a welded strand or cord with a relatively equal profile at the weld. This is hereafter referred to as “end-to-end welded” strands or cords. This solution does provide a strand or cord, which has inferior mechanical properties e.g. a lower force at rupture, a lower elasticity (strain at rupture), and higher bending stiffness and lower torsion ductility.
Although end-to-end welded metal strands can be used to provide cords, a sacrifice on mechanical properties of the metal cord is made.